Two dimensional graphical output is supported by a specialised form of
FrameSet called
a Plot, whose base Frame corresponds with the native coordinates of
the underlying graphics system. Plotting operations are specified in
physical coordinates which correspond with the Plot's current
Frame. Typically, this might be a celestial coordinate system.

Three dimensional plotting is also supported, via the Plot3D class -
sub-class of Plot.

Operations, such as drawing lines, are automatically transformed from
physical to graphical coordinates before plotting, using an adaptive
algorithm which ensures smooth curves (because the transformation is
usually non-linear). ``Missing'' coordinates (e.g. graphical
coordinates which do not project on to the celestial sphere),
discontinuities and generalised clipping are all consistently handled.
It is possible, for example, to plot in equatorial coordinates and
clip in galactic coordinates. The usual plotting operations are
provided (text, markers), but a geodesic curve replaces the primitive
straight line element. There is also a separate function for drawing
axis lines, since these are normally not geodesics.

In addition to drawing coordinate grids over an area of the sky, another
common use of the Plot class is to produce line plots such as flux
against wavelength, displacement again time, etc. For these
situations the current Frame of the Plot would be a compound Frame
(CmpFrame) containing a pair of 1-dimensional Frames - the first
representing the X axis quantity (wavelength, time, etc), and the second
representing the Y axis quantity (flux, displacement, etc). The Plot
class includes an option for axes to be plotted logarithmically.

Perhaps the most useful graphics function available is for drawing
fully annotated coordinate grids (e.g. the Figure below).

Figure:
A labelled coordinate grid for an all-sky zenithal equal area
projection in ecliptic coordinates. This was composed and drawn
via a Plot using a
single function call.

This uses a general algorithm which does not depend on knowledge of
the coordinates being represented, so can also handle
programmer-defined coordinate systems. Grids for all-sky projections,
including polar regions, can be drawn and most aspects of the output
(colour, line style, etc.) can be adjusted by setting
appropriate Plot attributes.

Further reading: For a more complete description of
Plots and how to produce graphical output, see . Also
see the Plot entry in .